Search

For the first time, we report a short channel high performance, gate-all-around strained Si 0.4 Ge 0.6 nanosheet PMOSFET with aggressively scaled dimensions. We demonstrate realization of s-Si 0.4 Ge 0.6 nanosheet with 5nm thickness and device with L G =25nm featuring record high I ON =508 µA/µm at I OFF =100nA/µm and V DS = -0.5V. This result is obtained with the combination of (a) novel Si-cap-free gate oxide solution featuring thin EOT=9.1A, low D IT and N IT for s-Si 0.4 Ge 0.6 channel, (b) record high hole mobility= 450 cm2/Vs owing to compressive strain imparted by Si 0.7 Ge 0.3 strain relaxed buffer (SRB), (c) low R EXT =150 Ω-µm due to highly active, strained source/drain SiGe process and novel p++ cap layer, (d) optimized source/drain tip and junction to minimize GIDL impact to I OFF . Additionally, the impact of operating temperature on GIDL and I OFF is comprehensively studied to prescribe optimal V CC range of operation for this technology.

We report a short channel high performance Ge PMOS integrated with Si NMOS in sequential monolithic 3D stacking. A layer transfer Ge PMOS with record I ON = 497 μA/μm at I OFF = 8nA/μm and I ON = 630 μA/μm at I OFF = 100nA/μm and V DS = -0.5V is achieved for the first time. Optimized design of metal gate and contact on bottom Si NMOS device layer, along with a low process thermal budget developed for Ge layer transfer and top Ge PMOS device fabrication, allow for sequential stacking with no degradation on each MOS device characteristics. Heterogeneous 3D stacked Ge-Si CMOS inverter is also successfully demonstrated with drive performance maintained on Ge PMOS and Si NMOS.

Perhaps the greatest challenge facing quantum computing hardware development is the lack of a high throughput electrical characterization infrastructure at the cryogenic temperatures required for qubit measurements. In this article, we discuss our efforts to develop such a line to guide 300mm spin qubit process development. This includes (i) working with our supply chain to create the required cryogenic high volume testing ecosystem, (ii) driving full wafer cryogenic testing for both transistor and quantum dot statistics, and (iii) utilizing this line to develop a quantum dot process resulting in key electrical data comparable to that from leading devices in literature, but with unprecedented yield and reproducibility.

We investigate the structural and quantum transport properties of isotopically enriched Si28/SiO228 stacks deposited on 300-mm Si wafers in an industrial CMOS fab. Highly uniform films are obtained with an isotopic purity greater than 99.92%. Hall-bar transistors with an oxide stack comprising 10 nm of Si28O2 and 17 nm of Al2O3 (equivalent oxide thickness of 17 nm) are fabricated in an academic cleanroom. A critical density for conduction of 1.75×1011cm-2 and a peak mobility of 9800cm2/Vs are measured at a temperature of 1.7 K. The Si28/SiO228 interface is characterized by a roughness of Δ=0.4nm and a correlation length of Λ=3.4nm. An upper bound for valley splitting energy of 480μeV is estimated at an effective electric field of 9.5 MV/m. These results support the use of wafer-scale Si28/SiO228 as a promising material platform to manufacture industrial spin qubits.

Quantum computing's value proposition of an exponential speedup in computing power for certain applications has propelled a vast array of research across the globe. While several different physical implementations of device level qubits are being investigated, semiconductor spin qubits have many similarities to scaled transistors. In this article, we discuss the device/integration of full 300mm based spin qubit devices. This includes the development of (i) a 28 Si epitaxial module ecosystem for growing isotopically pure substrates with among the best Hall mobility at these oxide thicknesses, (ii) a custom 300mm qubit testchip and integration/device line, and (iii) a novel dual nested gate integration process for creating quantum dots.

Reducing the delay of backend interconnects is critical in delivering improved performance in next generation computer chips. One option is to implement interlayer dielectric (ILD) materials with increasingly lower dielectric constant (k) values. Despite industry need, there has been a recent decrease in study and production of these materials in academia and business communities. We have generated a backbone and porogen system that allows us to control porosity from 0 to 60% volume, achieve k-values from 3.4 to 1.6, maintain high chemical stability to various wet cleans, and deliver uniquely high mechanical strength at a given porosity. Finite element modeling and experimental results demonstrate that further improvements can be achieved through control of the pore volume into an ordered network. With hopes to spur more materials development, this paper discusses some molecular design and nanoscale hierarchical principles relevant to making next generation low-k ILD materials.

Ultrastable glasses are generated by vapor deposition on substrates heated near the glass transition temperature (Tg), but it is unclear if the remarkable properties of such glasses are present in ultrathin (100 nm) films. Here, we demonstrate that the moduli of 50 nm thick N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPD) film can be increased from 1.5 to 2.5 GPa by simply increasing the temperature of the substrate during deposition with a maximum in modulus found at T/Tg = 0.94. This maximum in modulus is the same modulus obtained for very thin (15 nm) NPD films deposited at 295 K (T/Tg = 0.80). However, the modulus of films deposited at this lower temperature abruptly decreases to approximately 1.5 GPa for thicker films; the modulus from deposition at T/Tg = 0.94 is thickness independent. In addition to the thin film modulus, the substrate temperature significantly impacts the water uptake in NPD films. From QCM, the volume fraction of water at equilibrium with nearly saturated water vapor decreases from nearly 4% to less than 1% as the substrate temperature increases from T/Tg = 0.82 to T/Tg = 0.93. The substrate temperature provides a simple route to control mechanical properties and water uptake into vapor-deposited NPD, and these concepts are likely extendable to other organic electronic materials; the increased moduli and decreased water uptake could enable improved performance and lifetime of small molecule glasses for a variety of organic electronic applications.

To lower interconnect signal delay, the industry continues to work on the integration of low-k interlayer dielectrics (ILD). Porosity is often added to further reduce dielectric constant and significantly impact capacitance. These porous dielectric films are most commonly deposited via Chemical Vapor Deposition (CVD), delivering a random order to the pore structure. Disordered films suffer from a reduction in mechanical properties, which ultimately limits the maximum porosity obtained due to film collapse. Control of porosity, pore size distribution and pore geometry is needed to extend the porosity beyond conventional percolation thresholds. Here we present the case study of a periodic mesoporous organosilica (PMO) film. We optimize solution processing to obtain an ordered film and characterize the film porosity, pore size distribution, geometry and mechanical properties. The PMO film is tested in both a dual damascene and replacement back end integration flow.

The modulus and glass transition temperature (Tg) of ultrathin films of polystyrene (PS) with different branching architectures are examined via surface wrinkling and the discontinuity in the thermal expansion as determined from spectroscopic ellipsometry, respectively. Branching of the PS is systematically varied using multifunctional monomers to create comb, centipede, and star architectures with similar molecular masses. The bulk-like (thick film) Tg for these polymers is 103 ± 2 °C and independent of branching and all films thinner than 40 nm exhibit reductions in Tg. There are subtle differences between the architectures with reductions in Tg for linear (25 °C), centipede (40 °C), comb (9 °C), and 4 armed star (9 °C) PS for ≈ 5 nm films. Interestingly, the room temperature modulus of the thick films is dependent upon the chain architecture with the star and comb polymers being the most compliant (≈2 GPa) whereas the centipede PS is most rigid (≈4 GPa). The comb PS exhibits no thickness dependence in moduli, whereas all other PS architectures examined show a decrease in modulus as the film thickness is decreased below ∼40 nm. We hypothesize that the chain conformation leads to the apparent susceptibility of the polymer to reductions in moduli in thin films. These results provide insight into potential origins for thickness dependent properties of polymer thin films. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012

The effect of main chain stiffness and side chain flexibility on the elastic modulus and glass transition temperature (Tg) of thin polymer films is investigated using nontraditional polymers formed from 5-(2-phenylethylnorbornene). Depending on the polymerization route chosen, the resulting polymer backbone is comprised of either bicyclic (norbornyl) units, which leads to a relatively rigid polymer with a high bulk Tg, or monocyclic (cyclopentyl) units, which leads to a more flexible structure with a lower bulk Tg. The modulus and Tg of the rigid bicyclic polymer are thickness independent down to

Wetting on a corrugated surface that is formed via wrinkling of a hard skin layer formed by UV oxidation (UVO) of a poly(dimethylsiloxane) (PDMS) slab is studied using advancing and receding water contact angle measurements. The amplitude of the wrinkled pattern can be tuned through the pre-strain of the PDMS prior to surface oxidation. These valleys and peaks in the surface topography lead to anisotropic wetting by water droplets. As the droplet advances, the fluid is free to move along the direction parallel to the wrinkles, but the droplet moving orthogonal to the wrinkles encounters energy barriers due to the topography and slip-stick behavior is observed. As the wrinkle amplitude increases, anisotropy in the sessile droplet increases between parallel and perpendicular directions. For the drops receding perpendicular to the wrinkles formed at high strains, the contact angle tends to decrease steadily towards zero as the drop volume decreases, which can result in apparent hysteresis in the contact angle of over 100°. The wrinkled surfaces can exhibit high sessile and advancing contact angles (>115°), but the receding angle in these cases is generally vanishing as the drop is removed. This effect results in micrometer sized drops remaining in the grooves for these highly wrinkled surfaces, while the flat analogous UVO-treated PDMS shows complete removal of all macroscopic water drops under similar conditions. These wetting characteristics should be considered if these wrinkled surfaces are to be utilized in or as microfluidic devices.

Surface wrinkling was used to determine the elastic modulus at ambient temperature of polystyrene (PS) films of varying thickness and relative molecular mass ( M n ). A range of M n from 1.2 kg/mol to 990 kg/mol was examined to determine if the molecular size impacts the mechanical properties at the nanoscale. Ultrathin films exhibited a decrease in modulus for all molecular masses studied here compared to the bulk value. For M n > 3.2 kg/mol, the fractional change in modulus was statistically independent of molecular mass and the modulus began to deviate from the bulk as the thickness is decreased below ≈50 nm. An order of magnitude decrease in the elastic modulus was found when the film thickness was ≈15 nm, irrespective of M n . However, an increase in the length scale for nanoconfinement was observed as the molecular mass was decreased below this threshold. The modulus of thin PS films with a molecular mass of 1.2 kg/mol deviated from bulk behavior when the film thickness was decreased below ≈100 nm. This result illustrates that the modulus of thin PS films does not scale with molecular size. Rather, the quench depth into the glass appears to correlate well with the length scale at which the modulus of the films deviates from the bulk, in agreement with molecular simulations from de Pablo and coworkers [31] and recent experimental work [35] .

Planar capacitors can quickly test material properties of metals and dielectrics for interconnects. A sidewall capacitor device is used to evaluate metal thin-film barriers. Etch stop planar capacitors in turn can test multi-layer etch stops, exposing differences between leaky and good etch stop films. Fillable planar capacitors are also fabricated and results presented for that class of fill materials.

The RC delay and power restrictions imposed by the interconnect system can contribute to poor circuit performance in an increasingly severe manner as dimensions shrink. Resistances are increasing faster than the scale factor of the technology and capacitance improvements are constrained by mechanical requirements of the assembled stack. Collectively, these cause a bottleneck in both local and global information transfer on a chip. Novel deposition methods and novel conductor materials are being explored as means to increase conductive cross sectional area. Molecular ordering is an opportunity to simultaneously deliver capacitance and mechanical strength. Despite these improvement paths, a more holistic approach to interconnect design is needed, where the application and micro architecture are more tolerant of RC scaling constraints.

The wrinkling of a 50:50 blend of a high molecular mass (Mn = 990 kg/mol) and low molecular mass (Mn = 1.3 kg/mol) polystyrene (PS) film is studied as a function of annealing temperature and film thickness. Both thermal and mechanical wrinkling are utilized to elucidate the apparent modulus of these PS blend films. The PS blend shows a modulus comparable to the high molecular weight PS, ≈ 3.2 GPa for mechanical wrinkling at ambient and thermal wrinkling for T ≤ 50 °C. A sharp decrease in the apparent modulus of the film occurs when thermal wrinkling occurs at 60 °C or higher. The calculated modulus in this case is 0.5 GPa, which is significantly below the modulus determined the neat PS for either Mn when thermally wrinkled at T > 60 °C. This behavior is attributed to a combination of surface segregation of the low molecular weight PS as well as the large difference in bulk glass transition temperature (Tg) of each component. During thermal wrinkling, the high Mn PS vitrifies first, while the surface containing primarily low Mn PS is rubbery; this leads to only the underlayer of PS wrinkling initially and selection of a shorter wavelength due to the effective thickness. The increased thermally induced stresses during cooling when the low Mn PS is vitrified do not change the selected wavelength and instead only leads to an increase in the wrinkle amplitude. These results illustrate a potential method to modulate the wrinkle wavelength without changing the overlayer, which could be useful for patterning applications.

The mechanical stability of polymeric nanostructures is critical to the processing, assembly, and performance of numerous existing and emerging technologies. A key predictor of mechanical stability is the elastic modulus. However, a significant reduction in modulus has been reported for thin films and nanostructures when the thickness or size of the polymer material decreases below a critical length scale. Routes to mitigate or even eliminate this reduction in modulus, and thus enhancing the mechanically stability of polymeric nanostructures, would be extremely valuable. Here, two routes to modulate the mechanical properties of polymers at the nanoscale are described. Exposure to ultraviolet light and ozone (UVO) cross-links the near surface region of high molecular mass PS films, rendering the elastic modulus independent of thickness. However, UVO cannot eliminate the decrease in modulus of low molecular mass PS or PMMA due to limited reaction depth and photodegradation, respectively. Alternatively, the thickness dependence of the elastic modulus of both PS and PMMA can be eliminated by addition of dioctyl phthalate (DOP) at 5% by mass. Furthermore, an increase in modulus is observed for films with thicknesses less than 30 nm with 5% DOP by mass in comparison to neat PS. Although DOP acts as a plasticizer for both PS and PMMA in the bulk, evidence indicates that DOP acts as an antiplasticizer at the nanoscale. By maintaining or even increasing the elastic modulus of polymers at the nanoscale, these methods could lead to improved stability of polymeric nanostructures and devices.

The design of future generations of Cu-low-k dielectric interconnects with reduced electronic crosstalk often requires engineering materials with an optimal trade off between their dielectric constant and elastic modulus. This is because the benefits associated with the reduction of the dielectric constant by increasing the porosity of materials, for example, can adversely affect their mechanical integrity during processing. By using load-dependent contact-resonance atomic force microscopy, the changes in the elastic modulus of low-k dielectric materials due to processing were accurately measured. These changes were linked to alterations sustained by the structure of low-k dielectric films during processing. A two-phase model was used for quantitative assessments of the elastic modulus changes undergone by the organosilicate skeleton of the structure of porous and pore-filled dielectrics.

Periodic wrinkled surfaces have generated significant interest over the past decade as these structures can be easily fabricated over large areas with minimal fabrication cost, but these structures have generally been limited to thin films on soft elastomeric substrates, which limits their general applicability and utility. Here we present a simple methodology to generate wrinkled surfaces on rigid substrates by surface segregation of a photocatalyst. Upon ultraviolet light (UV) induced photopolymerization, increased catalyst concentration yields a cross-linked layer at the free surface that is supported on top of a more liquid-like bulk film due to differences in polymerization rate. Further polymerization of the underlayer provides the requisite mechanical stress (contraction due to polymerization) to create a wrinkled pattern. A system based upon the renewable monomer, furfuryl alcohol, that is cross-linked with a photoacid generator, triphenyl sulfonium triflate, is utilized to illustrate this concept. Moreover, the polymerized furfuryl alcohol can be transformed into amorphous carbon by heating at elevated temperatures in an inert environment. The role of photoacid generator concentration and substrate temperature on the wrinkle formation and morphology is presented. Finally, exposure through a simple mask can generate hierarchical structures with the wrinkled structure conforming to the geometric constraints of the photopatterned area, including curvilinear structures. This photocatalyzed surface segregation-based methodology provides a promising route to the facile fabrication of microstructured surfaces based upon the wrinkling instability.

The thin film mechanical properties of a series of glassy triarylamines [4,4′-N,N′-dicarbazole-biphenyl (CBP), N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) and N,N′-di-(1-naphthyl)-N,N′-diphenyl-1,1′-biphenyl-4-4′-diamine (NPD)], which are commonly used in organic light emitting devices (OLEDs), are examined using surface wrinkling to elucidate their elastic moduli at ambient temperature. As mechanical properties are closely associated with molecular packing and morphology, these measurements provide an effective route to study the correlation between the structure and the related thickness dependent morphology of organic thin films. For all molecular glasses examined in this article, the modulus remains statistically invariant for films thicker than 20 nm. However, a large variation in the modulus is observed for films thinner than 20 nm. This behaviour is found to be correlated with the bulk glass transition temperature (Tg) of the materials. For both CBP and TPD with Tg of approximately 60 °C, the modulus decreases by a factor of two when the thin film thickness is approximately 10 nm. Conversely, the modulus of NPD with Tg of 95 °C increases by nearly a factor of two with the decrease of film thickness to 20 nm or less, similar to the trend observed for tris(8-hydroxyquinolinato)aluminum (Tg = 175 °C). This work provides critical information to consider for the applications of organic electronic devices, which frequently use organic thin films with sub-50 nm thickness.

Elastic constants and cross-sectional dimensions of imprinted nanolines of poly(methyl methacrylate) (PMMA) on silicon substrates are determined nondestructively from finite-element inversion analysis of dispersion curves of hypersonic acoustic modes of these nanolines measured with Brillouin light scattering. The results for the cross-sectional dimensions, under the simplifying assumption of vertical sides and a semicircular top, are found to be consistent with dimensions determined from critical-dimension small-angle x-ray scattering measurements. The elastic constants C(11) and C(44) are found to be, respectively, 11.6% and 3.1% lower than their corresponding values for bulk PMMA. This result is consistent with the dimensional dependence of the quasi-static Young's modulus determined from buckling measurements on PMMA films with lower molecular weights. This study provides the first evidence of size-dependent effects on hypersonic elastic properties of polymers.

The intrinsic flexibility of organic molecular films has been suggested to enable bendable electronics in comparison to their stiffer, inorganic counterparts. However, very little is known regarding the mechanical properties of these molecular glasses that are commonly utilized in organic electronics. To begin to address these issues, the elastic modulus of vapor deposited tris(8-hydroxyquinolinato)aluminium (Alq3) films, commonly used in organic light emitting devices (OLEDs), is determined as a function of thickness from 10 nm to 100 nm using a wrinkling-based metrology. These thicknesses correspond well with the range actually utilized in OLEDs. The direct deposition of Alq3 onto a polydimethylsiloxane (PDMS) elastomer results in anomalous results due to diffusion of Alq3 into the PDMS substrate. Conversely, a thin polystyrene (PS) film can be used as a diffusion barrier, enabling the elastic moduli to be accurately measured. Similar to most organic glasses, the Young's modulus of Alq3 is on the order of 1 GPa and is statistically invariant for thicknesses >20 nm. Interestingly, there is a significant increase in the Young's modulus for thinner films. The modulus of a 10 nm Alq3 film is found to be nearly twice that of a thicker film. Corresponding to this change in modulus is a loss of the optical adsorption peak associated with aggregation of Alq3, which suggests that the modulus change is related to the local packing of the molecule. This result illustrates that the thickness of active layers in OLEDs impacts not only the device performance but also their elastic properties, both of which are important for use in flexible devices.